Branka Tucić

Phenotypic plasticity is widely acknowledged as one of the most common solutions for coping with novel environmental conditions following climate change. However, it is less known whether the current amounts of trait plasticity, which is sufficient for matching with the contemporary climate, will be adequate when global temperatures exceed historical levels. We addressed this issue by exploring the responses of functional and structural leaf traits in Iris pumila clonal individuals to experimentally increased temperatures (~1.5 °C) using an open top chamber (OTC) design. We determined the phenotypic values of the specific leaf area, leaf dry matter content, specific leaf water content, and leaf thickness in the leaves sampled from the same clone inside and outside of the OTC deployed on it, over seasons and years within two natural populations. We analyzed the data using a repeated multivariate analysis of variance, which primarily focusses on the profiles (reaction norms (RNs)) of a variable gathered from the same individual at several different time points. We found that the mean RNs of all analyzed traits were parallel regardless of experienced temperatures, but differed in the level and the shape. The populations RNs were similar as well. As the amount of plasticity in the analyzed leaf trait was adequate for coping with elevated temperatures inside the OTCs, we predict that it will be also sufficient for responding to increased temperatures if they exceed the 1.5 °C target.

Phenotypic plasticity is widely acknowledged as one of the most common solutions for coping with novel environmental conditions following climate change. However, it is less known wheth-er current amounts of trait plasticity, which is sufficient for matching with contemporary climate, will be adequate when global temperatures exceed historical levels. We addressed this issue by ex-ploring the responses of functional and structural leaf traits in Iris pumila clonal individuals to ex-perimentally increased temperature (~1.5°C), using an open top chamber (OTC) design. We de-termined phenotypic values of specific leaf area, leaf dry matter content, specific leaf water con-tent and leaf thickness in leaves sampled from the same clone inside and outside of the OTC de-ployed on it, over seasons and years within two natural populations. We analyzed the data by a repeated multivariate analysis of variance, which is primarily focused on profiles (reaction norms, RNs) of a variable gathered from the same individual at several different time points. We found that the mean RNs of all analyzed traits were parallel regardless of experienced temperatures, but differed in the level and the shape. The populations RNs were similar as well. Since the amount of plasticity in analyzed leaf trait was adequate for coping with elevated temperatures inside the OTCs, we predict that it will be also sufficient for responding to increased temperatures if they exceed the 1.5°C target.

Directional asymmetry is a systematic difference between the left and right sides for structures with bilateral symmetry or a systematic differentiation among repeated parts for complex symmetry. This study explores factors that produce directional asymmetry in the flower ofIris pumila, a structure with complex symmetry that makes it possible to investigate multiple such factors simultaneously. The shapes and sizes of three types of floral organs, the falls, standards, and style branches, were quantified using the methods of geometric morphometrics. For each flower, this study recorded the compass orientations of floral organs as well as their anatomical orientations relative to the two spathes subtending each flower. To characterize directional asymmetry at the whole‐flower level, differences in the average sizes and shapes according to compass orientation and relative orientation were computed, and the left–right asymmetry was also evaluated for each individual organ. No size or shape differences within flowers were found in relation to anatomical position; this may relate to the terminal position of flowers inIris pumila, suggesting that there may be no adaxial–abaxial polarity, which is very prominent in many other taxa. There was clear directional asymmetry of shape in relation to compass orientation, presumably driven by a consistent environmental gradient such as solar irradiance. There was also clear directional asymmetry between left and right halves of every floral organ, most likely related to the arrangement of organs in the bud. These findings indicate that different factors are acting to produce directional asymmetry at different levels. In conventional analyses not recording flower orientations, these effects would be impossible to disentangle from each other and would probably be included as part of fluctuating asymmetry.

We tested the hypothesis that sharing essential resources through interconnected ramets increases stress tolerance of a clonal plant in patchy environments. A number of circle-shaped clones of Iris pumila naturally growing in a sunexposed habitat were selected and cut into two equal halves with different integration status: one with intact and the other with disconnected rhizomes. One-half of each clone was then shaded with a neutral screen to provide 50% of ambient irradiance, so that one-half of both clones consisted of connected and disconnected halves (referred to as ?clone quarters?). Leaves collected from each clone quarter were analyzed for malondialdehyde (MDA) content (a stress indicator) and the values of three functional traits, specific leaf area (SLA), leaf dry matter content (LDMC) and leaf water content (LWC). MDA content was greater in unshaded (more stressed) than in shaded (less stressed) leaves. All three morphological traits changed with light gradient, but only SLA was impacted by the ramet integration status. SLA and MDA tended to be inversely related in each clone quarter, indicating a (compensatory) mechanism utilized by I. pumila plants in coping with environmental stress. SLA and LDMC were highly negatively correlated in general, but less strongly in interconnected ramets compared to those with a disrupted connection. The results suggest that intraclonal physiological integration confers a fitness benefit to I. pumila plants in heterogeneous environments, likely by balancing two fundamental plant activities - rapid biomass production and nutrient conservation.

The angiosperm flower is a complex integrated phenotype, but within this structure there are partly independent units or modules. The interconnections among floral organ traits are hypothesized to be mostly generated by pollinatormediated selection. In this study, we explore whether floral dry mass per area (DMA) in an insect-pollinated herb, Iris pumila, exhibits a modular correlation pattern as has been reported for some size-related traits. We found that the overall pattern of floral organ integration with regard to DMA was uneven in the offspring of Iris pumila derived from a sunexposed and a shaded natural population. Since principal component analysis (PCA) showed that most of the eigenvalue variance was explained by the first two principal components (PCs), these PCs were considered as two floral modules. The greatest factor loadings on the first PC axis was that of the perianth and style arm DMA (PSDMA) and perianth tube DMA (PTDMA),while on the second PC axis, the greatest factor loading was that of stamen DMA (STDMA). The results indicate that the function of the first module would be to attract a pollinating vector, while the second one would reflect male functions. Selection analyses revealed that the targets of phenotypic selection were both intra-floral integration and individual floral traits. Both PSDMA and PC1DMA were under strong linear selection, while PTDMA experienced direct stabilization selection. The level of integration in floral organ DMA expressed in the term of relative eigenvalue variance appeared to be rather low, as was documented for other angiosperm taxa.

Does Environmentally Contingent Variation in the Level of Molecular Chaperones Mirror a Biochemical Adaptation to Abiotic Stress? | IntechOpen, Published on: 2011-08-29. Authors: Branka Tucić, Sanja Manitašević Jovanović and Ana Vuleta

Ambient light significantly influences the structural and physiological characteristics of Iris pumila leaves. A random sample of Iris clones native to an exposed site at the Deliblato Sands, Serbia was partially covered with a neutral screen that transmitted 35% of daylight, so that each clone experienced reduced and full sunlight at the same time. The sun-exposed leaves were significantly thicker, had greater stomatal density, exhibited higher lipid peroxidation, increased activities of SOD, APX, CAT enzymes and higher contents of non-enzymatic antioxidants (anthocyanins and phenols) and water deficit relative to shade-leaves. The activities of GR, GPX, and GST enzymes was unaffected by the irradiance level.

Plasticity to irradiance and genotypic correlations between structural and physiological leaf traits in Iris pumila were investigated in an experiment conducted at a sun-exposed dune habitat in the Deliblato Sands. A sample of six native, genetically different clones were covered with a neutral screen which transmitted ~35% of daylight, so that one clone-half of each clone experienced reduced sunlight, while the other one full sunlight. LMA, stomatal density, ?leaf, enzymatic and non-enzymatic antioxidants and lipid peroxidation were determined in unshaded and shaded leaves of the same clone. It was found that the plasticity index, PIv was higher for physiological than for structural traits. Genotypic correlations between trait pairs were high, but rarely significant, in contrast to the correlation matrices which were significantly different between unshaded and shaded leaves.

The level of homosexual behaviour is evaluated in one laboratory population of seed beetle and derived lines selected to reproduce early (E) or late in life (L), where inadvertent selection for either low or high heterosexual activity has been detected. The magnitudes of homosexual interaction, measured as chasing and mounting individuals of the same sex, are estimated over different age classes. These magnitudes are correlated with previously observed levels and patterns of age‐specific variation of heterosexual activity of both sexes in the E and L experimental lines. The results obtained support the perception error hypothesis proposing that a low degree of sexual discrimination is genetically correlated with high sexual activity. The fitness costs of the same‐sex interactions are tested by assessing their effects on longevity. In both sexes, the longevities of homosexual pairs are reduced relative to individually‐housed virgin beetles in both the E and L lines, although homosexual interactions have a more pronounced effect on male survival than on female survival. Although the results obtained suggest that the longevity cost of homosexual interactions can be substantial, this cost is much smaller than the cost of heterosexual interactions.